fix(NODE-4133): array field NestedPaths return type (#3184)

Author: boenfu

src/mongo_types.ts

@@ -496,7 +496,7 @@ export type NestedPaths<Type> = Type extends
   | { _bsontype: string }
   ? []
   : Type extends ReadonlyArray<infer ArrayType>
-  ? [number, ...NestedPaths<ArrayType>]
+  ? [] | [number, ...NestedPaths<ArrayType>]
   : Type extends Map<string, any>
   ? [string]
   : // eslint-disable-next-line @typescript-eslint/ban-types

test/types/community/collection/filterQuery.test-d.ts

@@ -204,6 +204,14 @@ expectNotType<Filter<PetModel>>({ 'playmates.0.name': 123 });
 expectNotType<Filter<PetModel>>({ 'laps.foo': 'string' });
 expectNotType<Filter<PetModel>>({ 'treats.0': 123 });
 
+/// it should not accept wrong types for nested document array fields
+expectError<Filter<PetModel>>({
+  treats: {
+    $elemMatch: true
+  }
+});
+expectError<Filter<PetModel>>({ treats: 123 });
+
 // Nested arrays aren't checked
 expectNotType<Filter<PetModel>>({ 'meta.deep.nestedArray.0': 'not a number' });